3.2 Calculating Mass of Substances

What is the mass of 0.25 moles of hydrated copper(II) sulfate, CuSO₄.5H₂O?

Relative formula mass (M_r):  H₂O = 18  CuSO₄ = 160

2.7 g aluminium reacts with 38.1 g of iodine, I₂, to make 40.8 g aluminium iodide, AlI₃.

Relative atomic masses (A_r):     Al = 27        I = 127

Relative formula mass (M_r):      AlI₃ = 408

What coefficients would balance the equation for the reaction?

Nitrogen and hydrogen react together to make ammonia.

N₂ + 3H₂  → 2NH₃

If 2.0 g of hydrogen is added to 12.0 g of nitrogen which substance is the limiting reactant and how much of the excess reactant remains?

Relative atomic masses (A_r): H = 1    N = 14

	Limiting Reactant	Mass of excess reactant
A	nitrogen	2.0 g
B	nitrogen	10.0 g
C	hydrogen	2.7 g
D	hydrogen	9.3 g

A solution of CuSO₄ has a concentration of 35 g/dm³.

What mass of CuSO₄ would there be in 250 cm³ of the solution?